September 20, 2023

Industrial seaweed will not cool the climate or save nature, new report says

Research shows that mass seaweed plantations pose a major threat to marine ecosystems and are unlikely to capture or permanently store significant quantities of carbon.

September 20, 2023 - A report published today by the international research organization ETC Group casts serious doubts on seaweed as an emerging “blue carbon” industry. Their research shows that mass seaweed plantations pose a major threat to marine ecosystems and are unlikely to capture or permanently store significant quantities of carbon.[1]

This report, The Seaweed Delusion: Industrial seaweed will not cool the climate or save nature, is published just as Seafields and Running Tide, both for-profit companies aiming to launch marine geoengineering seaweed projects, have undertaken the first seaweed biomass sinking trials. ETC Group’s research shows that experiments like these pose new threats to the ocean ecosystems where they are being conducted. These companies are using the same German vessel that was used for Lohafex, a marine geoengineering experiment that was widely rejected by civil society in 2009 and finally suspended because of strong opposition.

“In a bid to get investors, governments and communities on their side, the multi-million dollar   ‘big seaweed’ corporations are telling a salty story of being clean, green and development-friendly” said Jim Thomas, one of its co-authors.

“In reality massive algae plantations will introduce new risks to already stressed marine ecosystems and may threaten small-scale algae cultivators’ livelihoods. Our research suggests that under a blue-green varnish, potential social and ecological impacts of industrial seaweed will do more harm than good to our planet”, he added.

Scientific evidence shows that taking the whole production cycle into account, industrial seaweed ecosystems could lead to more CO2 in the atmosphere, not less.

For example, a study published in the ICES Journal of Marine Science found that “seaweed ecosystems are natural carbon sources, releasing on average around 20 tonnes per square kilometer every year. But it could be much higher still. … We estimate it could be potentially as high as 150 tonnes emitted to the atmosphere per km² every year.”[2]

In fact, there is no clear evidence of seaweed farms being able to directly contribute to long-term carbon sequestration – but the industry is still lobbying to profit from selling carbon credits from industrial seaweed projects on the back of this myth.

Carbon credits and offsets are widely opposed by climate justice movements as they have not had any effect on slowing down climate change. On the contrary, they provide a means for big polluters to justify continuing to emit greenhouse gases.

“Mass algae cultivation and the sinking of seaweed, like other geoengineering carbon removal projects, will bring a whole new set of environmental and social consequences. Like tree monoculture plantations and other false “solutions”, they will divert resources and attention from the measures necessary to keep the UNFCCC Paris Agreement goal of staying below 1.5°C. Industrial seaweed. Mass algae farming is a dangerous distraction from what must be top priority: to cut carbon emissions swiftly, especially in the global North”, said Silvia Ribeiro, Latin America Director at ETC Group.

“Our report shows that the US$15 billion global seaweed market is currently dominated by agribusiness traders and ingredients giants such as Cargill, Kerry Group, FMC and DowDuPont. It is important to remember that today peasant farmers still feed the equivalent of 70% of the world’s people with less than 30% of the world’s land, water and agricultural resources. Handing over coastal areas to agro-industry giants will only increase land and water grabs and hamper people’s capacity to feed themselves”, said Neth Daño, ETC Group´s Asia Director.

Seaweed provides multiple ecosystem functions that help maintain healthy biological and human communities. Wild seaweed gatherers and fisherfolk point out that, in this way, seaweed has already been ‘saving the planet’ for millennia and provided livelihood for coastal communities that are now threatened by this new industrial initiative.

Heeding both science and warnings from seaweed gatherers and Indigenous Peoples, it is time to put a halt to the seaweed bandwagon and instead ensure that the world’s precious natural seaweed commons are properly protected”, warned the authors of the new report.


Media contact:
Laura Dunn: +1 514 607 9979
Silvia Ribeiro:
Neth Daño:

[1] Since the 2015 Paris Agreement on Climate Change, the global seaweed industry has bloomed with hundreds of new startups designed to grow, harvest, transform, or sink up to 500 million tons of seaweed biomass, a business boosted by hundreds of millions of dollars in investment. Even though algae has been commercially cultivated in Asia since the fifties, the sector has now launched a global offensive on very different terms, diving into the big salty promise of carbon finance.
[2] 29 Gallagher J. B., Shelamoff V., Layton C. (2022). Seaweed ecosystems may not mitigate CO2 emissions. ICES Journal of Marine Science, 79: 585–592.

More related to this issue:
Turn around the Geo-engineering ship to protect the moratorium!
LOHAFEX Update: Throwing precaution (and iron) to the wind (and waves)
LOHAFEX Update: Geo-engineering ship plows on as Environment Ministry calls for a halt

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